I find that on the computer i am able to type just as fast as I can think. When I start writing it's like I'm just thinking and I'm not even aware of my fingers flying across the keyboard. Recently I was stuck somewhere for like and hour and I pulled out some paper and started writing a scene for this novel I am working on. I felt like I was going in slow motion because writing by hand takes forever. When I was a kid however, I wrote all of my stories by hand and didnt have a problem with it. It was once I got to college and got accustomed to typing that I made the switch to writing on the computer.
I like to write with my hand when coming up with the initial idea. I see the difference between using a pen and a typewriter as the same difference between using a knife or a gun. One is way more personal, the other gets the job done quicker.
I like pens because I like seeing the progression of replacing and editing words instead of just erasing them.